Quasi-Schreier Domains II

We study a class of integral domains characterized by the property that every nonzero finite intersection of principal ideals is a directed union of invertible ideals.     

Almost Integrally Closed Domains

Abstract

A domain R is called almost integrally closed if R is integrally closed in R _P for each nonzero P ∈ Spec(R). Arbitrary quasilocal domains of (Krull) dimension 1 and arbitrary integrally closed domains are examples of almost integrally closed domains. There are no other examples in the contexts of Noetherian, one-dimensional or pseudo-valuation domains, as a consequence of the fact that any almost integrally closed domain that is not integrally closed has at most one height 1 prime ideal. However, a pullback example shows that a non-integrally closed domain that is almost integrally closed need not be semiquasilocal or of dimension at most 1. By analyzing the behavior of the almost integrally closed property for CPI-extensions, we obtain a characterization of the almost integrally closed locally divided domains. Applications are given to the case of G-domains. It also follows that if a divided domain R is not a field, then R is almost integrally closed if and only if some (resp., each) nonzero P ∈ Spec(R) is such that R _P is almost integrally closed and R is integrally closed in R _P .     

Monoid Domain Constructions of Antimatter Domains

An integral domain without irreducible elements is called an antimatter domain. We give some monoid domain constructions of antimatter domains. Among other things, we show that if D is a GCD domain with quotient field K that is algebraically closed, real closed, or perfect of characteristic p > 0, then the monoid domain D[X; ?⁺] is an antimatter GCD domain. We also show that a GCD domain D is antimatter if and only if P^?1 = D for each maximal t-ideal P of D.     

Constructing Almost Excellent Unique Factorization Domains

Abstract

Let (T, M) be a complete local normal integral domain containing the rationals such that |T/M | ≥ c where c is the cardinality of the real numbers. Let p be a non-maximal prime ideal of T such that _{T p} is a regular local ring. We construct a local Unique Factorization Domain (UFD) A such that the M-adic completion of A is T, p is maximal in the generic formal fiber and all fibers of A are geometrically regular except for those over some height one prime ideals.

     

Integrally Closed Domains,Minimal Polynomials,and Null Ideals of Matrices

Abstract

We show that every element of the integral closure D′ of a domain D occurs as a coefficient of the minimal polynomial of a matrix with entries in D. This answers affirmatively a question of Brewer and Richman, namely, if integrally closed domains are characterized by the property that the minimal polynomial of every square matrix with entries in D is in D[x]. It follows that a domain D is integrally closed if and only if for every matrix A with entries in D the null ideal of A, N _D (A)?=?{f?∈?D[x]?∣?f(A)?=?0} is a principal ideal of D[x].     

t-Schreier Domains

We study, under the name t-Schreier, the class of those integral domains whose group of t-invertible t-ideals satisfies the Riesz interpolation property. The so-called Prüfer v-multiplication domains (PVMDs) and Prüfer domains are special cases of t-Schreier domains. We show that, while a number of results known for Prüfer domains and PVMDs hold for these domains, the t-Schreier domains have a remarkable capability of unifying various results in that the results proved for t-Schreier domains can also be translated to results on pre-Schreier domains and hence on GCD and Bezout domains.     

局部几乎完全整环的几点注记

整环$R$被称为局部几乎完全整环, 指的是对任意极大理想${\frak m}$都有$R_{{\frak m}}$是几乎完全整环. 本文利用局部完全环, 几乎投射模, 弱内射模, 几乎强平坦模和强Matlis余挠模给出了局部几乎完全整环的若干等价刻画.     

On the Witt Vectors of Perfect Rings in Positive Characteristic

The purpose of this article is to prove some results on the Witt vectors of perfect F _p -algebras. Let A be a perfect F _p -algebra for a prime integer p, and assume that A has the property P. Then does the ring of Witt vectors of A also have P? A main theorem gives an affirmative answer for P = ″integrally closed” under a very mild condition.     

Minimal Overrings of an Integrally Closed Domain

Abstract

The main purpose of this paper is to characterize minimal overrings of an integrally closed domain R. We show that there exists a strong relationship between minimal overrings and the notion of ideal transforms. In particular, we prove that if T(M) = S(M) for each maximal ideal M, then there is a bijective correspondence between the set of invertible maximal ideals of R and the set of minimal overrings of R. This study enables us to produce several interesting applications concerning semi-local, Dedekind, Prüferian and Krull domains. Moreover, we investigate the spectrum of a minimal overring in comparison with the spectrum of R, and we determine whether the polynomial ring R[X ₁, X ₂,…, X _n ] has a minimal overring.     

A Note on Multiplicative Ideal Theory

We state a semigroup version of (19.15)THEOREM and (36.2)THEOREM, and disprove (30.9)THEOREM of Gilmers book [3] for commutative semigroups. We give a condition for the Kronecker function ring D* with respect to a star-operation * on an integral domain D to be well-defined.2000 Mathematics Subject Classification: Primary 13A15 Secondary 20M14.     

The number of overrings of an integrally closed domain

We establish in this work a result that gives the number of overrings for any integrally closed domain that has only finitely many overrings; then we provide an algorithm to compute this number. We end this paper with an open problem for integral domains that are not necessarily integrally closed.     

Counting intermediate rings in normal pairs

Let RS be an extension of integral domains. If each intermediate ring in this extension is integrally closed in S, then (R,S) is called a normal pair. We investigate in this work the set of intermediate rings in such ring extensions. We establish several results and equations concerning the cardinality of the set of intermediate rings. In particular, we give a way to compute the number of intermediate rings in normal pairs with only finitely many intermediate rings.     

第四类华罗庚域的Bergman核函数

本文给出了第四类华罗庚域H EIV上的Bergman核函数,全纯自同构群以 及semi—Reinhardt域上的完备标准正交函数系.     

Lip_J-扩张域和一致域(英文)

本文证明了如下两个结果:(1)域D(?)R~n是一致域当且仅当D是Lip_J-扩张域;(2)Jordan域D(?)R~2是拟圆当且仅当对在D上满足|f′(z)|≤d(z,(?)D)~(-1)的任意的解析函数f恒有f∈Lip_J(D),其中J(x_1,x_2)=1/2 log(1+|x_1-x_2|/d(x_1,(?)D))(1+|x_1-x_2|/d(x_2,(?)D)),x_1,x_2∈D.     

John域

本文研究了Ｊｏｈｎ域，证明了有界一致域必定是Ｊｏｈｎ域和Ｊｏｈｎ域是拟共形不变量．